This invention regards a power tong. More particularly, it regards a power tong without a radial opening, the power tong being particularly well suited for use during installation of piping when drilling in the ground, such as is known from e.g. petroleum production. The tong has a swivel coupling surrounding the tong for transferring pressurized fluid from an external source of pressurized fluid to the tong when the tong rotates about the longitudinal axis of the pipe.
It is known, among other things from petroleum production, to use power tongs for installing and dismantling lengths of piping to or from a pipe string associated with a drilling rig. It is common to use mechanical pipe tongs that, following the screwing or unscrewing of a pipe joint, on the whole are moved horizontally away from the pipe string, the pipe string being located at the drilling centre of the drill rig.
This method is dependent on the power tong having a radial opening, whereby the power tong can be displaced in the horizontal plane when being removed from the pipe string.
Having this type of radial opening in a power tong that has to be able to rotate about the longitudinal axis of the pipe obviously complicates the design of the power tong. The opening weakens the structure surrounding the pipe considerably. As a result, the structure must be up-rated in order to accommodate the relatively large forces being transferred between the power tong and the pipe string. A relatively complicated mechanical device is required to close the radial opening when the power tong is in use, and in many cases also to transfer forces between the sides of the opening.
The object of the invention is to remedy or diminish at least one of the disadvantages of prior art.
The object is achieved in accordance with the invention, by the characteristics stated in the description below and in the following claims.